Maintaining Online Redo Log Files
log file status解读:
CURRENT->表明当前oracle正在往里面写redo log data
INACTIVE->表明当前的日志文件组已经可以被覆盖了、或者可以被archived.表明其已经发生检查点.
FAST_START_MTTR_TARGET参数指定了oracle在规定的参数值内，必须进行一次DBWn操作.
SQL> show parameter FAST_START NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ fast_start_io_target integer 0 fast_start_mttr_target integer 0 fast_start_parallel_rollback string LOW SQL> alter system set FAST_START_MTTR_TARGET=300 scope=both; System altered. SQL> show parameter FAST_START NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ fast_start_io_target integer 0 fast_start_mttr_target integer 300 fast_start_parallel_rollback string LOW SQL>
SQL> alter system switch logfile; System altered.
SQL> alter system checkpoint; System altered.
新增日志组、新增日志组成员
SQL> set line 200 SQL> select * from v$logfile; GROUP# STATUS TYPE MEMBER IS_ ---------- ------- ------- -------------------------------------------------- --- 3 ONLINE /u01/app/oracle/oradata/testdb/redo03.log NO 2 ONLINE /u01/app/oracle/oradata/testdb/redo02.log NO 1 ONLINE /u01/app/oracle/oradata/testdb/redo01.log NO SQL> l 1* alter database add logfile group 4 ('/u01/app/oracle/oradata/testdb/redo04.log') size 100M SQL> / Database altered. SQL> select * from v$logfile order by 1; GROUP# STATUS TYPE MEMBER IS_ ---------- ------- ------- -------------------------------------------------- --- 1 ONLINE /u01/app/oracle/oradata/testdb/redo01.log NO 2 ONLINE /u01/app/oracle/oradata/testdb/redo02.log NO 3 ONLINE /u01/app/oracle/oradata/testdb/redo03.log NO 4 ONLINE /u01/app/oracle/oradata/testdb/redo04.log NO SQL>
SQL> alter database add logfile member '/u01/app/oracle/oradata/testdb/redo04a.rdo' to group 4; Database altered. SQL> select * from v$logfile order by 1; GROUP# STATUS TYPE MEMBER IS_ ---------- ------- ------- -------------------------------------------------- --- 1 ONLINE /u01/app/oracle/oradata/testdb/redo01.log NO 2 ONLINE /u01/app/oracle/oradata/testdb/redo02.log NO 3 ONLINE /u01/app/oracle/oradata/testdb/redo03.log NO 4 INVALID ONLINE /u01/app/oracle/oradata/testdb/redo04a.rdo NO 4 ONLINE /u01/app/oracle/oradata/testdb/redo04.log NO SQL>
注意:往一个组里添加成员，不需要指定大小；默认按照其他现有成员大小创建.
删除日志组
SQL> select group#,thread#,sequence#,status from v$log; GROUP# THREAD# SEQUENCE# STATUS ---------- ---------- ---------- ---------------- 1 1 55 INACTIVE 2 1 56 INACTIVE 3 1 57 ACTIVE 4 1 58 CURRENT SQL> alter database drop logfile member '/u01/app/oracle/oradata/testdb/redo04a.rdo'; alter database drop logfile member '/u01/app/oracle/oradata/testdb/redo04a.rdo' * ERROR at line 1: ORA-01609: log 4 is the current log for thread 1 - cannot drop members ORA-00312: online log 4 thread 1: '/u01/app/oracle/oradata/testdb/redo04.log' ORA-00312: online log 4 thread 1: '/u01/app/oracle/oradata/testdb/redo04a.rdo'
SQL> alter system switch logfile; System altered. SQL> select group#,thread#,sequence#,status from v$log; GROUP# THREAD# SEQUENCE# STATUS ---------- ---------- ---------- ---------------- 1 1 59 CURRENT 2 1 56 INACTIVE 3 1 57 ACTIVE 4 1 58 ACTIVE SQL> alter database drop logfile member '/u01/app/oracle/oradata/testdb/redo04a.rdo'; Database altered. SQL> select * from v$logfile order by 1; GROUP# STATUS TYPE MEMBER IS_ ---------- ------- ------- -------------------------------------------------- --- 1 ONLINE /u01/app/oracle/oradata/testdb/redo01.log NO 2 ONLINE /u01/app/oracle/oradata/testdb/redo02.log NO 3 ONLINE /u01/app/oracle/oradata/testdb/redo03.log NO 4 ONLINE /u01/app/oracle/oradata/testdb/redo04.log NO SQL>
11203ora-> rm -rf redo04a.rdo
SQL> alter database drop logfile member '/u01/app/oracle/oradata/testdb/redo04.log'; alter database drop logfile member '/u01/app/oracle/oradata/testdb/redo04.log' * ERROR at line 1: ORA-00361: cannot remove last log member /u01/app/oracle/oradata/testdb/redo04.log for group 4 SQL>
- An instance requires at least two groups of online redo log files;
- An active or current group cannot be dropped.
- When an online redo log file group is dropped,the operating system files are not deleted.
SQL> alter database drop logfile group 4; Database altered. SQL> select group#,thread#,sequence#,archived,status from v$log; GROUP# THREAD# SEQUENCE# ARC STATUS ---------- ---------- ---------- --- ---------------- 1 1 59 NO CURRENT 2 1 56 YES INACTIVE 3 1 57 YES INACTIVE SQL>
Relocate & Rename
You can use operating system commands to relocate redo logs,then use the ALTER DATABASE statement to make their new names(locations) known to the database.This procedure is necessary,for example,if the disk currently used for some redo log files is going to be removed,or if datafiles and a number of redo log files are stored on the same disk and should be separated to reduce contention.
To rename redo log members ,you must have the ALTER DATABASE system privilege.Additionally,you might also need operating system privileges to copy files to the desired location and privileges to open and backup the database.
Before relocating your redo logs,or making any other structural changes to the database,completely back up the database in case you experience problems while performing the operation.As a precaution,after renaming or relocating a set of redo log files,immedidately backup the database control file.
方法一:alter database rename file command
0.执行rename之前，数据库文件信息
SQL> select * from v$logfile order by 1; GROUP# STATUS TYPE MEMBER IS_ ---------- ------- ------- -------------------------------------------------- --- 1 ONLINE /u01/app/oracle/oradata/testdb/redo01.log NO 2 ONLINE /u01/app/oracle/oradata/testdb/redo02.log NO 3 ONLINE /u01/app/oracle/oradata/testdb/redo03.log NO SQL> alter database add logfile group 4 ('/u01/app/oracle/oradata/testdb/redo04.log') size 50M; Database altered. SQL> select * from v$logfile order by 1; GROUP# STATUS TYPE MEMBER IS_ ---------- ------- ------- -------------------------------------------------- --- 1 ONLINE /u01/app/oracle/oradata/testdb/redo01.log NO 2 ONLINE /u01/app/oracle/oradata/testdb/redo02.log NO 3 ONLINE /u01/app/oracle/oradata/testdb/redo03.log NO 4 ONLINE /u01/app/oracle/oradata/testdb/redo04.log NO
1、shutdown the database
SQL> shutdown immediate; Database closed. Database dismounted. ORACLE instance shut down.
2、copy the online redo log files to the new location
11203ora-> cp redo04.log .. 11203ora-> ll total 2520580 -rw-r----- 1 oracle oinstall 9814016 Jul 15 11:50 control01.ctl -rw-r----- 1 oracle oinstall 209723392 Jul 15 11:50 DATACENTER01.dbf -rw-r----- 1 oracle oinstall 362422272 Jul 15 11:50 example01.dbf -rw-r----- 1 oracle oinstall 52429312 Jul 15 11:50 redo01.log -rw-r----- 1 oracle oinstall 52429312 Jul 15 10:31 redo02.log -rw-r----- 1 oracle oinstall 52429312 Jul 15 11:06 redo03.log -rw-r----- 1 oracle oinstall 52429312 Jul 15 11:50 redo04.log -rw-r----- 1 oracle oinstall 209723392 Jul 15 11:50 rman_ts01.dbf -rw-r----- 1 oracle oinstall 650125312 Jul 15 11:50 sysaux01.dbf -rw-r----- 1 oracle oinstall 765468672 Jul 15 11:50 system01.dbf -rw-r----- 1 oracle oinstall 30416896 Jul 15 10:14 temp01.dbf -rw-r----- 1 oracle oinstall 120594432 Jul 15 11:50 undotbs01.dbf -rw-r----- 1 oracle oinstall 15736832 Jul 15 11:50 users01.dbf 11203ora-> cd .. 11203ora-> ll total 51208 -rw-r----- 1 oracle oinstall 52429312 Jul 15 11:51 redo04.log drwxr-x--- 2 oracle oinstall 4096 Jul 15 11:50 testdb
3、place the database in mount mode
SQL> startup mont; SP2-0714: invalid combination of STARTUP options SQL> startup mount; ORACLE instance started. Total System Global Area 430075904 bytes Fixed Size 2229064 bytes Variable Size 327158968 bytes Database Buffers 92274688 bytes Redo Buffers 8413184 bytes Database mounted.
4、execute the command
SQL> alter database rename file '/u01/app/oracle/oradata/testdb/redo04.log' to '/u01/app/oracle/oradata/redo04.log'; Database altered.
5、open database for normal operation
SQL> alter database open; Database altered.
6、查看新的日志组信息
SQL> select * from v$logfile order by 1; GROUP# STATUS TYPE MEMBER IS_ ---------- ------- ------- -------------------------------------------------- --- 1 ONLINE /u01/app/oracle/oradata/testdb/redo01.log NO 2 ONLINE /u01/app/oracle/oradata/testdb/redo02.log NO 3 ONLINE /u01/app/oracle/oradata/testdb/redo03.log NO 4 ONLINE /u01/app/oracle/oradata/redo04.log NO
alter database rename file '$ORACLE_HOME/ORADATA/testdb/log2a.rdo' to '$ORACLE_HOME/ORADATA/log1c.rdo';
方法二:add new members and drop old members.
查询日志组
SQL> select group#,thread#,sequence#,archived,status from v$log; GROUP# THREAD# SEQUENCE# ARC STATUS ---------- ---------- ---------- --- ---------------- 1 1 59 NO CURRENT 2 1 56 YES INACTIVE 3 1 57 YES INACTIVE SQL>
SQL> select * from v$logfile order by 1; GROUP# STATUS TYPE MEMBER IS_ ---------- ------- ------- -------------------------------------------------- --- 1 ONLINE /u01/app/oracle/oradata/testdb/redo01.log NO 2 ONLINE /u01/app/oracle/oradata/testdb/redo02.log NO 3 ONLINE /u01/app/oracle/oradata/testdb/redo03.log NO SQL>
What is Redo Threads?
When speaking in the context of multiple database instance,the redo log for each database instance is also referred to as a redo thread.In typical configurations,only one database instance accesses an Oracle Database,so only one thread is present.In an Oracle Real Application Clusters environment,however,two or more instance concurrently access a single database and each instance has its own thread of redo.A separate redo thread for each instance avoids contention for a single set of redo log files,thereby eliminating a potential performance bottleneck.
Redo File 配置
How Redo Files Work
Online Redo log files are used in a cyclic fashion
When a online redo log file is full,LGWR will move to the next log group.
- - Called a log switch(The act of switching from one log file group to the other is called a log switch)
- - Checkpoint operation also occurs
- - Information written to the control file
A checkpoint is the writing of dirty(modified) blocks from the buffer cache to disk.
log switch 一定会引发 checkpoint ，但相反不成立。
When will LGWR write redo?
- When a transaction commits
- Every three seconds
- When the Redo Log Buffer becomes one-third full
- When there is more than a megabyte of changed records in the Redo Log Buffer.
- Before the DBWn writes modified blocks in the Database Buffer Cache to the data files.
ASM管理存储---新增日志组
alter database add logfile group 4 ('+DATA_DG_A/orcl/onlinelog/group_4_01.log','+DATA_DG_B/orcl/onlinelog/group_4_02.log') size 512M; alter database add logfile group 5 ('+DATA_DG_A/orcl/onlinelog/group_5_01.log','+DATA_DG_B/orcl/onlinelog/group_5_02.log') size 512M; alter database add logfile group 6 ('+DATA_DG_A/orcl/onlinelog/group_6_01.log','+DATA_DG_B/orcl/onlinelog/group_6_02.log') size 512M;
SQL> select * from v$logfile order by 1,4; GROUP# STATUS TYPE MEMBER IS_RECOVE ---------- --------------------- --------------------- ------------------------------------------------------------ --------- 1 ONLINE +DATA_DG_A/orcl/onlinelog/group_1.261.852573709 NO 1 ONLINE +DATA_DG_B/orcl/onlinelog/group_1_02.log NO 2 ONLINE +DATA_DG_A/orcl/onlinelog/group_2.262.852573745 NO 2 ONLINE +DATA_DG_B/orcl/onlinelog/group_2_02.log NO 3 ONLINE +DATA_DG_A/orcl/onlinelog/group_3.263.852573779 NO 3 ONLINE +DATA_DG_B/orcl/onlinelog/group_3_02.log NO 6 rows selected.
SQL> alter database add logfile group 4 ('+DATA_DG_A/orcl/onlinelog/group_4_01.log','+DATA_DG_B/orcl/onlinelog/group_4_02.log') size 512M; Database altered. SQL> select * from v$logfile order by 1,4; GROUP# STATUS TYPE MEMBER IS_RECOVE ---------- --------------------- --------------------- ------------------------------------------------------------ --------- 1 ONLINE +DATA_DG_A/orcl/onlinelog/group_1.261.852573709 NO 1 ONLINE +DATA_DG_B/orcl/onlinelog/group_1_02.log NO 2 ONLINE +DATA_DG_A/orcl/onlinelog/group_2.262.852573745 NO 2 ONLINE +DATA_DG_B/orcl/onlinelog/group_2_02.log NO 3 ONLINE +DATA_DG_A/orcl/onlinelog/group_3.263.852573779 NO 3 ONLINE +DATA_DG_B/orcl/onlinelog/group_3_02.log NO 4 ONLINE +DATA_DG_A/orcl/onlinelog/group_4_01.log NO 4 ONLINE +DATA_DG_B/orcl/onlinelog/group_4_02.log NO 8 rows selected.
SQL> alter database add logfile group 5 ('+DATA_DG_A/orcl/onlinelog/group_5_01.log','+DATA_DG_B/orcl/onlinelog/group_5_02.log') size 512M; Database altered. SQL> select * from v$logfile order by 1,4; GROUP# STATUS TYPE MEMBER IS_RECOVE ---------- --------------------- --------------------- ------------------------------------------------------------ --------- 1 ONLINE +DATA_DG_A/orcl/onlinelog/group_1.261.852573709 NO 1 ONLINE +DATA_DG_B/orcl/onlinelog/group_1_02.log NO 2 ONLINE +DATA_DG_A/orcl/onlinelog/group_2.262.852573745 NO 2 ONLINE +DATA_DG_B/orcl/onlinelog/group_2_02.log NO 3 ONLINE +DATA_DG_A/orcl/onlinelog/group_3.263.852573779 NO 3 ONLINE +DATA_DG_B/orcl/onlinelog/group_3_02.log NO 4 ONLINE +DATA_DG_A/orcl/onlinelog/group_4_01.log NO 4 ONLINE +DATA_DG_B/orcl/onlinelog/group_4_02.log NO 5 ONLINE +DATA_DG_A/orcl/onlinelog/group_5_01.log NO 5 ONLINE +DATA_DG_B/orcl/onlinelog/group_5_02.log NO 10 rows selected.
SQL> alter database add logfile group 6 ('+DATA_DG_A/orcl/onlinelog/group_6_01.log','+DATA_DG_B/orcl/onlinelog/group_6_02.log') size 512M; Database altered. SQL> select * from v$logfile order by 1,4; GROUP# STATUS TYPE MEMBER IS_RECOVE ---------- --------------------- --------------------- ------------------------------------------------------------ --------- 1 ONLINE +DATA_DG_A/orcl/onlinelog/group_1.261.852573709 NO 1 ONLINE +DATA_DG_B/orcl/onlinelog/group_1_02.log NO 2 ONLINE +DATA_DG_A/orcl/onlinelog/group_2.262.852573745 NO 2 ONLINE +DATA_DG_B/orcl/onlinelog/group_2_02.log NO 3 ONLINE +DATA_DG_A/orcl/onlinelog/group_3.263.852573779 NO 3 ONLINE +DATA_DG_B/orcl/onlinelog/group_3_02.log NO 4 ONLINE +DATA_DG_A/orcl/onlinelog/group_4_01.log NO 4 ONLINE +DATA_DG_B/orcl/onlinelog/group_4_02.log NO 5 ONLINE +DATA_DG_A/orcl/onlinelog/group_5_01.log NO 5 ONLINE +DATA_DG_B/orcl/onlinelog/group_5_02.log NO 6 ONLINE +DATA_DG_A/orcl/onlinelog/group_6_01.log NO GROUP# STATUS TYPE MEMBER IS_RECOVE ---------- --------------------- --------------------- ------------------------------------------------------------ --------- 6 ONLINE +DATA_DG_B/orcl/onlinelog/group_6_02.log NO 12 rows selected.
